1. Technical Field of the Invention
The present invention relates to a semiconductor device, a method for manufacturing the same, a circuit substrate, an electro-optical apparatus, and electronic equipment.
2. Description of the Related Art
Conventionally, so-called Au bumps are frequently used for mounting semiconductor devices, e.g., driver ICs. In the formation of the Au bump, a seed layer made of TiW/Au or the like is sputtered on a semiconductor element, a resist is patterned and, thereafter, Au electroplating is applied up to a height on the order of 20 μm. However, it is predicted that stable formation of bumps, such as formation of a resist having a high aspect ratio, etching of a seed layer, and the like, becomes difficult with a reduction in the pitch of the electrodes of the above-described driver IC.
In recent years, an inexpensive electroless Ni bump was developed in response to the reduction in pitch. However, this bump is harder than the Au bump and, therefore, may be unsuitable, particularly for COG (Chip On Glass) techniques in which the driver IC is directly mounted on a display panel, from the viewpoint of the reliability of connection.
Japanese Unexamined Patent Application Publication No. 2-272737 discloses a technology in which resin protrusions are disposed in the locations at a distance from electrodes, connection patterns for serving as conductive layers are disposed to cover and connect the surfaces of the protrusions and the electrodes and, thereby, protrusion electrodes are provided. According to this technology, protrusion electrodes having small diameters can easily be formed, and a reduction in semiconductor chip size is facilitated. In addition, the stress during mounting is absorbed because the resin protrusions have elasticity and, therefore, stabilization in mounting quality is facilitated.
However, the above-described known technology has problems as described below.
In the formation of the protrusion electrodes, it is necessary to perform patterning after a semiconductor element is coated with a resin, form a conductive layer by sputtering or the like and, furthermore, pattern the resulting conductive layer. In the known patterning, since a desired shape is given by, for example, photo-etching, a photomask or the like suitable for the desired shape must be prepared on an etching step basis and, therefore, the manufacturing cost is increased. There is a further problem in that fine patterning is required for both of the resin layer and the conductive layer, and the manufacturing process becomes complicated.
When a plurality of protrusions are formed by photo-etching, the spacings between protrusions may be formed into tapered shapes. In this case, the spacings between base portions of the protrusions become small, and it may become difficult to respond to a reduction in the pitch of the protrusions.
The present invention was made in consideration of the above-described points. It is an object of the present invention to provide a semiconductor device and a method for manufacturing the same capable of simplifying the manufacturing process and responding to a reduction in pitch, and to provide a circuit substrate, an electro-optical apparatus, and electronic equipment.